This invention relates generally to batteries, and more particularly to batteries comprising an assembly of electrochemical cells in a novel housing.
Assemblies of electrochemical cells interconnected in series and positioned in containers are known to the art. Such battery assemblies can be used as an energy source in a variety of applications, for example personal computers, cellular telephones, video camcorders, and the like. The batteries may use primary (i.e. non-rechargeable) such as alkaline cells, or secondary (i.e. rechargeable) such as nickel/metal hydride cells.
Batteries for computers, cellular phones and other applications are presently packaged in many ways. Generally, they are placed within an injection molded, two piece, plastic container, or in a shrink wrapped plastic tube that encases the battery cells. These packaging means present some notable shortcomings. For example, injection molded plastic housings generally must be formed with rather thick walls. Typically, a minimum housing wall thickness of about 0.7 millimeters is encountered.
Electrochemical cells contain chemically active substances which react with each other to generate electricity. For any given application, it is desirable to use cells having the largest possible size, whereby to enable the greatest amount of derivable energy to be available. Accordingly, for many applications, standard housing walls can not be employed because the size of an encased assembly of electrochemical cells of sufficient size to provide the required energy would be too large to fit within the space of the electrical device for which it is intended.
Conventional housings, such as injection molded housings, can present significant costs of manufacture, particularly for fabricating housings having comparatively thin walls. In the case of shrink wrapping, a thin wall battery housing can be provided at a relatively low cost. However, a shrink wrap battery assembly will often have bulbous protrusions, wrinkling, or other undesired features which can interfere with the intended use of the encased assembly, and which may necessitate burdensome and costly repackaging of the cell assembly. For example, bulbous protrusions and other undesired topography can result in the shrink wrap cell assembly having a non-uniform thickness that renders the assembly too large to fit within the allocated space of an electrical device. Shrink wrapped items, especially those with such features, are also aesthetically undesirable.
Further, as a consequence of the manner in which a shrink wrap housing is formed, the cell housing generally can only be of a shape that directly corresponds to the shape of the one or more encased battery cells. This effectively precludes use of shrink wrap cell housings for many applications. For example, it is often desirable or necessary to form a groove or other defined element on the outer surface of the housing. Such features are commonly used for orientation. Other surface features, not possible when a shrink wrap is used, may include devices for ensuring proper loading, for interlocking the cell assembly into the device, for displaying an element through a window in the electrical device, and the like.
It would, therefore, be desirable to have a battery housing that has relatively uniform and exceptionally thin walls. It would further be desirable to have such a battery housing wherein desired topography can be formed on the housing surface.
The present invention provides a novel battery assembly that includes a housing with walls having uniform and extremely small cross-sectional thickness (e.g., less than 0.7 millimeters) and which has a good visual appearance. In another aspect the invention provides a method for forming such battery assemblies and housings therefore.
The invention is based in part on the discovery that an extrusion molding process can produce a plastic battery cell housing, including a housing of a generally rectangular sleeve shape, which has a thin and uniform wall structure and an aesthetically pleasing exterior. Further, the use of such extrusion molding process enables cell housings to be manufactured at relatively low cost.
These and other features and objects of the invention will be readily understood from the following detailed description of the invention which should be read in light of the accompanying drawings.